The principle of stabilizing contact lenses with lower bearing surface, such as that which is shown in FIGS. 1 and 2 appended hereto, is known.
“Lower bearing surface” indicates that the lower edge 1 is sufficiently thick to butt against the edge of the lower eyelid, without passing beneath, unlike the upper edge 3 which, for its part, is “thin”, that is to say suitable for passing beneath the upper eyelid.
Because of the abutment of the lower edge of the lens on the edge of the lower eyelid, the possibility is obtained of causing the lens to translate upward when looking downward: this is called “translation” of the lens on the eye.
Moreover, because of this difference of thickness and hence of weight between its lower and upper edges, the lens tends to retain its orientation relative to the eye, that is to say not to turn relative to the latter: it is said that the lens is “stabilized”.
These stabilization and translation features make it possible to produce lenses comprising different optical correction zones, the movement of the eye from one to the other of these various zones being obtained by movement of the eye upward or downward.
Such lenses with multiple correction zones may notably be lenses with several focal lengths, used for correcting farsightedness.
To increase the translation of the lens, it is known practice to cut off the lower edge 1, as can be seen in FIG. 1 appended hereto: this lower edge has a curve corresponding substantially to that of the edge of the lower eyelid, thereby forming a sort of flat helping to limit the risks of rotation of the lens on the eye and hence promote stabilization.
These lenses with lower bearing surface, which have a dissymmetry between their upper and lower portions, differ notably from the symmetrical lenses used for the correction of astigmatism, such as, for example, the lens of document EP0742462.
More precisely, while these lenses with lower bearing surface comprise a single bearing surface, placed in the lower portion of the lens, lenses such as that which is described in EP0742462 have two symmetrical bearing surfaces allowing the lens to be held in a centered position relative to the eye (no translation of the lens relative to the eye is desired).
Because of its relative thickness, the lower edge of the lenses with lower bearing surface may create discomfort and lesser physiological tolerance.